Heating arrangement for internal combustion engines



United States Patent 3,450,977 HEATING ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES Heinz Krauss, Stuttgart-Unterturkheim, Germany, assignor to Robert Bosch G.m.b.H., Stuttgart, Germany Filed July 11, 1966, Ser. No. 564,284 Claims priority, application Germany, July 14, 1965, B 82,824 Int. Cl. H02p 9/10, 11/00 U.S. Cl. 322-33 7 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an arrangement for heating spark plugs of internal combustion engines whereby the temperature of the spark plugs is maintained substantially constant under varying load conditions of the engine.

For the purpose of achieving reliable operation of internal combustion engines, it is desirable to regulate the temperatures of spark plugs so that they are not too cold at starting or low load conditions, or too high during heavy load conditions. For example, if the temperature of the spark plugs is insufficient, it is possible that the spark plugs will fail to operate. On the other hand, if the temperature of the spark plugs is too high, a condition that may prevail under heavy engine load conditions, the spark plugs may become destroyed.

Temperature regulatory systems applied for such purposes in internal combustion engines, are per se, not new. However, such systems, heretofore, were based upon electrical heating circuits which operated in conjunction with a plurality of resistors that were switched in and out of the circuit depending upon a prevailing load condition of the engine. The use of such resistors, in this manner results in considerable power losses and, accordingly, high drainage of the battery used to energize the circuit. Furthermore, such heating systems, in the prior art, have complex switching arrangements which do not provide smooth regulation in a fully automatic manner.

Accordingly, it is an object of the present invention to provide a heating arrangement for spark plugs in an internal combustion engine whereby the temperature of the spark plugs is maintained substantially constant irrespective of the load conditions of the engine.

Another object of the present invention is to provide a heating arrangement for internal combustion engines, as set forth, which regulates the temperature of the spark plugs in a fully automatic manner.

Another object of the present invention is to provide a heating arrangement, of the character described, which operates on the basisof inductive electrical elements to avoid power losses resulting when equivalent resistor elements are used.

Yet another object of the present invention is to provide a heating arrangement for spark plugs of internal combustion engines, as set forth, whereby temperature 3,450,977 Patented June 17, 1969 regulation of the spark plugs is accomplished in a smooth manner.

Still another object of the present invention is to provide an arrangement, of the character described, which is adapted to operate in conjunction with internal combustion engines using light or heavy fuels.

A further object of the present invention is to provide a heating arrangement for spark plugs of internal combustion engines, as set forth, adaptable to operate in conjunction with engines having a large number of cylinders.

Yet a further object of the present invention is to provide a heating arrangement for use in internal combustion engines, of the character described, having fault detection means whereby malfunctioning of a spark plug is indicated.

A still further object of the present invention is to provide a heating arrangement for spark plugs in internal combustion engines, which is reliable in operation, requires no maintenance, and may be manufactured simply and economically.

With these object in view, the present invention includes a synchro generator having a rotor winding and a multiphased stator inductively linked to the rotor, each phase of the stator being connected to one or more spark plugs for heating the same, and a temperature sensor situated within the vicinity of the spark plug to detect the temperature thereof. The temperature sensor is conneced to the rotor of the synchro generator and provides current thereto which is inversely related to the temperature prevailing at the spark plugs. An electrical amplifier may be interposed between the temperature sensor and the rotor of the synchro generator so as to supply current thereto and not load excessively the temperature sensor. The heating arrangement also includes an indicating lamp which serves as a fault detecting means and which lights up to inform operating personnel when a spark plug malfunctions.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing, which is an electrical schematic diagram of an exemplary embodiment of the invention.

Referring to the drawing, the heating arrangement illustrated therein is designed to operate in conjunction with a six-cylinder internal combustion engine. The spark plugs associated with these cylinders are grouped in groups 10, 12 and 13. Each of these groups is connected to a phase of a three-phase synchro generator 14. The latter operates in conjunction with a power supply in the form of a battery 15, a protective charging switch 16 therefor, a main switch 17, and a relay 18. A synchro generator, as commonly known in the art, has a rotor winding 14a and a stator winding 14b. The stator has in turn three coils X, Y and Z displaced from each other by in space. When the rotor winding 14a is energized from a suitable power source, each of these coils connected at a common point, generate voltages x, y and 1 which are 120 out of phase with each other. Accordingly, the combination of the three voltages x, y and z determine, at any instant, the position of the rotor of the synchro in space. Synchro generators are widely used for automatic control purposes, and their theory and manner of operation are well known to those skilled in the art.

The energizing of the rotor winding 14a is accomplished by way of a control circuit 19 which includes a transistor 19a. The transistor operates cooperatively with a temperature regulating element 1%, and the regulating elements and 19d. The regulating voltage of the element 1% is derived from a voltage divider 20 consisting of the resistors 20a and 20b. These resistors of the voltage divider 20 are, in turn, connected to a temperature sensor 25 mounted preferably in the vicinity of the spark plug in one of the cylinders. A lamp 21 and a resistor 22 connected in parallel therewith, serves to provide indications for the purpose of controlling the heating arrangement of the present invention, when the starting motor 23 has started the engine 26. Once the engine has been properly started, the DC generator 24 will deliver charging current to the battery 15, by way ofthe protective switching means 16. When the direct current generator 24 is thus operating, it energizes the coil 180 of relay 18, and causes, thereby, the movable switching element of the relay to connect with the contact 18a.

To operate the heating arrangement of the present invention, the movable element 17a of the switch 17, is manually transferred to the contact 1%. In this position of the switch 17, direct current flows from the positive terminal of the battery to the common connection of the synchro stator coils, by way of the normally open contact 18b of the relay 18. As a result, the voltage potentials x, y and 1 provided by the stator coils are of equal magnitude and are applied to the spark pluggroups 10, 12 and 13. The spark plugs are, therefore, subjected in the conventional manner to a preheating process.

In order to start the thus preheated engine, the movable switching element 17a is moved along the contact 17b until it also engages the contact 17c. As a result, the motor 23 is energized and drives, in turn, the generator 24 and the synchro generator 14. The mechanical interconnection of the motor 23, direct current generator 24 and synchro generator 14, is shown by the dotted line in the drawing. This mechanical interconnection may be accomplished by suitable gearing coupled to the drive shafts of these three rotary components. The direct-current generator 24 applies a voltage, by way of path 24a, to the control circuit 19, and to the resistor 20b by way of the additional path 24b. Under this set of conditions, the spark plugs continue to be heated by way of the relay contact 18b. When the motor 23 commences to rotate. the voltage across the battery 15 may drop as a result of its internal resistance. This voltage drop, however, may be compensated, in the conventional manner, by appropriately bridging a starting resistor.

Once the motor 23 operates at a substantial speed, the volt-age output of the generator 24 becomes sufiicient to energize the coil of relay 18 and move, thereby, the switching element 18b into engagement with the contact 18a. As a result, the comon connection of the stator coils is connected to the opposite or negative pole of the battery by way of the indicating lamp 21 and the resistor 22 connected in parallel therewith. Since the negative terminal of the battery is also at zero or ground potential, the stator coils of the synchro generator now supply alternating current potentials to the spark plug groups 10, 12 and 13. The alternating currents in the stator coils X, Y and Z are derived from the rotary action of the synchro generator rotor. Thus, the magnetic field of the rotor cuts the coils X, Y and Z in a sequential manner so that alternating currents 120 apart in phase are induced within the coils. Once the direct current generator 24 and the synchro generator 14 are operating in this manner, these alternating current voltages are continuously applied to the spark plug groups independently of the position of the switch 17. Thus, once the engine has been star-ted and brought to proper speed, the switch 17 may be reset to the position shown in the drawing.

In order to maintain the temperature of the spark plugs within the range of 1050i50 C. under varying load conditions of the engine, it is essential that the rotor current of the synchro generator be regulated so that the current is decreased when heavier loads are encountered, and increased under lighter load conditions. This variation of the current through the rotor 14a, causes corresponding variations in the induced currents derived from coils X, Y and Z, and is regulated by the control circuit 19. The control circuit is provided for this purpose, with the power transistor 19a and the regulating elements and 19d for heavy and light load conditions, respectively. The control circuit is also provided with the temperature regulating element 19!).

The temperature sensing element 25 is, as indicated supra, located in the vicinity of the spark plugs so that it is subjected to the temperature prevailing thereat. The sensor 25, furthermore, is of the commonly-known type which as a negative coefii-cient so that it exhibits a greater resistance when subjected to a lower temperature. Acoordingly, if the temperature of the spark plugs should drop, the resistance of the sensor 25 is increased, and hence the voltage drop across the sensor, is thereby, also increased. As a result, a higher potential is applied to the resistors 20a and 20b, as well as the temperature regulating element 1%, by way of the path 25a. The emitter current of transistor 19a and consequently the current within the rotor 14a is, thereby, increased and this causes, in turn, the currents in the stator coils to be increased correspondingly. Such increase in the currents x, y, and z operate to heat further the spark plugs and thus increase their temperature. Accordingly, a drop in the temperature of the spark plugs as sensed by the element 25, is accompanied by a heating eifect of the spark plugs tending to return them to the desired temperature. The heating arrangement of the present invention, therefore, regulates itself automatically to maintain the temperature of the spark plugs substantially constant at the desired temperature.

In a similar manner, any rise in temperature sensed by the element 25, results in a decrease of the voltage potentials x, y and z. Thus the temperature sensor 25, in conjunction with the three-phase coils of the synchro generator 14, form a regulating circuit which can be compensated, if necessary, through the insertion of series and/or parallel resistors into the circuits of the X, Y, Z coils. For safety purposes, two cylinders may be provided with one temperature sensor each. If now the regulating circuit is controlled by the maximum value of the two sensors, then the regulating arrangement remains functional in the event that one of the temperature sensors fails to operate.

If the regulating circuit is designed to provide a heat ing rate of 40 watts with a battery having 24 volts across its terminals, the regulating circuit may be adapted for use with 12 volt spark plugs by switching a resistor into the path between the main switch 17 and the contact 18b. With such resistors switched into the circuit, the potentials x, y and z delivered by the stator of the synchro generator, are reduced to one-half of their values which prevail when 24 volt spark plugs are used. In effect, the resistor drops the battery voltage from 24 volts to onehalf this value or 12 volts.

The use of the synchro generator 14 within the regulating circuit provides also a fault detection system. For example, when one of the spark plug groups 10, 12 or 13 fails to operate or becomes short-circuited, the loading of the synchro generator is distributed so that the potential existing at the common connection of the stator coils, lights up the indicating lamp 21. With the indicating lamp in such a lighted state, operating personnel are immediately informed that a malfunction has occurred, and, accordingly, remedial action may be taken. An improved fault location system may be further obtained by providing a suitable indicator in conjunction with each of the branches X, Y and Z. With such an arrangement, then, it is possible to determine immediately the specific location of themalfunction as well.

The spark plug heating arrangement of the present invention is also adaptable to engines with a number of cylinders other than six. Thus, in the event that the engine has eight cylinders, each spark plug group 10, 12 and 13 would include three spark plugs with one of such spark plugs being replaced by a load-resistor. The latter provides the same loading eifect as a spark plug, and the stator coils are balanced as if nine spark plugs are in service even though only eight are actually present. When dealing with engines having a large number of cylinders it is especially desirable to use a generator having six or more stator phases. In such cases, it is necessary to retain only the relay 18 with contacts 18a and 18b. Similarly, the heating arrangement is also adaptable to the t'Ise of bipolar spark plugs. Their use, however, requires that precautionary insulation steps be taken with regard to the power supplies corresponding to adjacent poles, of these bipolar spark plugs.

While the invention has been illustrated and described as embodied in spark plugs for a plurality of engine cylinders, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any Way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of the prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention, and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An engine heating arrangement for heating at least one engine part adapted to be heated electrically, comprising voltage generating means coupled to said engine and electrically connected to said part to provide electrical current for heating thereof; a temperature sensor associated with said part to sense the temperature thereof; said'temperature sensor having internal electrical resistance with negative temperature coefficient so that said internal resistance increases when the temperature applied to said resistance decreases; and means connecting the temperature sensor to said voltage generating means so that the heating current provided therefrom maintains the temperature of said part constant under varying load conditions of said engine.

2. An engine heating arrangement for heating at least one engine part adapted to be heated electrically, comprising voltage generating means coupled to said engine and electrically connected to said part to provide electrical current for heating thereof; a temperature sensor associated with said part to sense the temperature thereof; means connecting the temperature sensor to said voltage generating means so that the heating current provided therefrom maintains the temperature of said part constant under varying load condition of said engine; and amplifying means included in said means connecting said temperature sensor to said voltage generating means.

3. An engine heating arrangement for heating at least one engine part adapted to be electrically heated, comprising a starter battery adapted to supply electric current during standstill of the engine; electric current generating means adapted to generate current during operation of the engine; and means for connecting the engine part to be heated with the starter battery during standstill of the engine whenever desired and for connecting said engine part to be heated with said electric current generating means during operation of said engine.

4. The engine heating arrangement of claim 3, wherein said electric current generating means is a synchro generator.

5. The engine heating arrangement of claim 3, wherein the positive pole of said starter battery is connected to said part to be heated when said engine is at standstill.

6. The engine heating arrangement according to claim 3 including means for automatically disconnecting said starter battery from said part to be heated whenever said engine commences to operate.

7. The engine heating arrangement accordingto claim 4, wherein the stator windings of said synchro generator are included in the conductor means leading from the starter battery to said part to be heated.

References Cited UNITED STATES PATENTS 1,099,365 6/1914 Henderson 219-209 X 2,158,733 5/1939 Sola 219 202 X ORIS L. RADER, Primary Examiner. H. H'UBERFELD, Assistant Examiner.

US. Cl. X.R. l23179; 219205, 209, 494; 32281 

